What questions should be asked to assess a patient's functional capacity in metabolic equivalents (METs)?

Questions to Ask for Assessing METs (Functional Capacity)

Ask patients if they can climb two flights of stairs or walk up a hill without symptoms—this single question identifies the critical 4 MET threshold that predicts perioperative cardiac risk. 1, 2

Core Questions Based on the 4 MET Threshold

The most clinically relevant cutoff is 4 METs, as patients unable to achieve this level have significantly increased perioperative cardiac and long-term risks 1. Structure your assessment around this threshold:

Activities Associated with <4 METs (Poor Functional Capacity):

• Can you take care of yourself (eating, dressing, bathing, using the toilet)?
• Can you walk indoors around your house?
• Can you walk 1-2 blocks on level ground at 2-3 mph?
• Can you do light housework like dusting or washing dishes?
• Can you play a musical instrument while sitting?
• Can you golf using a cart?
• Can you do slow ballroom dancing?

1, 3

Activities Associated with ≥4 METs (Adequate Functional Capacity):

• Can you climb a flight of stairs or walk up a hill? (5.5 METs)
• Can you walk on level ground at 4 mph?
• Can you run a short distance? (8 METs)
• Can you do heavy housework like scrubbing floors or moving heavy furniture? (8 METs)
• Can you do yard work like raking leaves or pushing a power mower? (4.5 METs)
• Can you participate in moderate recreational activities like golf (walking), bowling, dancing, doubles tennis? (6 METs)

1, 4

Activities Associated with >10 METs (Excellent Functional Capacity):

• Can you participate in strenuous sports like swimming, singles tennis, football, basketball, or skiing?

3, 2, 3

Structured Assessment Approach

Primary Screening Question:

"Can you walk 4 blocks or climb 2 flights of stairs without stopping?"

This question has been validated in 600 consecutive patients undergoing noncardiac surgery, where the inability to perform these activities predicted perioperative myocardial ischemia and cardiovascular events even after adjusting for other risk factors 1. The likelihood of serious complications was inversely related to blocks walked (P=0.006) or stairs climbed (P=0.01) 1.

Formal Assessment Tools:

Duke Activity Status Index (DASI) provides weighted scoring for 12 specific activities 1:

1. Self-care activities (2.75 METs)
2. Walking indoors (1.75 METs)
3. Walking 1-2 blocks on level ground (2.75 METs)
4. Climbing stairs or walking uphill (5.50 METs)
5. Running short distance (8.00 METs)
6. Light housework (2.70 METs)
7. Moderate housework like vacuuming (3.50 METs)
8. Heavy housework (8.00 METs)
9. Yard work (4.50 METs)
10. Sexual relations (5.25 METs)
11. Moderate recreational activities (6.00 METs)
12. Strenuous sports (7.50 METs)

The DASI has been validated and shows reasonable correlation with measured functional capacity in women (r=0.31, p=0.0002) and is a significant independent predictor even after adjusting for cardiac risk factors 5.

Clinical Interpretation Framework

Functional Capacity Classification 1, 6:

• Excellent: >10 METs
• Good: 7-10 METs
• Moderate: 4-6 METs
• Poor: <4 METs
• Unknown: Unable to estimate

Risk Stratification:

• ≥4 METs without symptoms: Proceed with planned surgery without further cardiovascular testing in most cases 6, 7
• <4 METs: Increased perioperative cardiac and long-term risk; consider further evaluation based on clinical risk factors and surgery type 1, 2

Important Caveats

Self-reported METs frequently overestimate actual functional capacity. In lung resection surgery patients, only 25% of subjective MET estimates correlated with objective measurements (κ=-0.107, P=0.02), with most patients overestimating their capacity 8. Similarly, in abdominal surgery patients, correlations between self-reported METs and risk assessment tools were weak (Spearman's ρ=-0.1 to -0.3), though the simple stair-climbing question showed better associations 9.

The stair-climbing question remains the most reliable single screening tool despite these limitations, as it has been prospectively validated in large perioperative cohorts and directly predicts outcomes 1.

Dependent functional status (requiring assistance with activities of daily living) is associated with significantly increased perioperative morbidity and mortality independent of MET level 1.

In highly functional asymptomatic patients (those who can perform >4 METs activities without symptoms), management rarely changes based on further cardiovascular testing, making it appropriate to proceed with surgery 6, 7.